Anti-atherogenic functions of HDL include mediation of reverse chlolesterol transport, and control of oxidation and inflammation. Mounting evidence supports the concept that HDL function can be impaired or lost, and that dysfunctional HDL contributes to the development of atherosclerosis. Familial hypercholesterolemia (FH) is an autosomal dominant disorder associated with severely elevated LDL levels and increased risk of premature coronary artery disease. The focus of therapy has been appropriately on the elevated LDL levels, but residual risk for cardiovascular events remains high, even with statin therapy. We have recently discovered that the HDL from patients with FH exacerbates inflammatory macrophage responses in vitro. A goal of this proposal (Specific Aim 1) is to examine the hypothesis that HDL of FH patients is dysfunctional (pro-inflammatory. pro-oxidant. or associated with reduced efflux capacity). Isoprostanes (IsoP) are formed from the non enzymatic oxidation of arachidonic acid in phospholipids of lipoproteins and cell membranes. Plasma levels of F2-S0P are accurate in vivo markers of lipid peroxidation and oxidant stress. Interestingly, the esterified IsoP in human plasma are mainly localized to HDL, with lesser amounts associated with LDL and VLDL. Several lines of evidence support a direct role for lipid peroxidation and F2-IS0P formation in atherosclerotic lesion development. At present it is unknown whether the accumulation of esterified F2-IS0P in HDL affects its atheroprotective functions. Interestingly, we have found that plasma from subjects with FH undergoing LDL apheresis has twice the amount of F2-IS0P compared to normal plasma, and that the apheresis decreases F2-IS0P levels by 45%. Isolevuglandins (IsoLG) are a group of y-ketoaldehydes (isoketals) that are highly reactive mediators of oxidative damage and are formed in parallel with isoprostanes. The reactivity of IsoLCB toward protein lysyl residues is much greater compared to that of malondialdehyde (IVIDA), which is known to reduce apoAI's ability to promote cholesterol efflux. We will investigate whether these bioactive lipids play direct mechanistic roles in the pro-inflammatory properties of HDL in FH. In Specific Aim 2, we will examine the hypothesis that accumulation of IsoP and reactive carbonyls (IsoLG and MDA) in HDL of FH patients results in loss of anti-inflammatory function. Recent evidence suggests that HDL regulates its atheroprotective functions in part by acquiring, transporting, and delivering microRNAs. Interestingly, the HDL microRNA profile is dramatically altered in homozygous FH. We will examine the hypothesis that HDL microRNAs are altered in hetFH and influence HDL function. Our results may lead to the development of new markers of HDL function, provide new pharmacologic targets for improving HDL function, and identify HDL as a target of therapy in FH patients